jbrob007

Carl & Mark,

Thanks for the info... #1. I dont need the cooling effects although a cooler engine is probably better - especially summertime. # 2. A COOL setup is always a factor! # 3. "Wont go fast enough 'legally' to receive effective downforce..." True, true... For arguments sake at what speed does it become effective? If I ever lose the middle of my chin spoiler I may use this as an alternative and effective air management would just be another plus Cause every now and again... ya know... we shark owners... tend to... uhhhhmmmm... ya know... perform Italian Tuneups...

Carl Fausett

That depends on what constitutes "effective" for you. We started to see measurable notice the first down force as low as 20 MPH, but the scales were very sensitive. Picking a number... say 100 pounds of down force as a an "effective" quantity, then about 40 MPH we had that.

mark kibort

you had 100lbs of downforce at 40mph??? I dont see how that is possible. can you explain? if so, what was the rear downforce at 40mph?
generally, you can easily plot and extrapolate from lower MPH to higher mph.

as an example. if you are getting 100lbs of downforce at 40mph, at 80mph you will get 400lbs and then at 160mph you would have 1600lbs of downforce.
(something close to this)

wings are easy to predict . my cup wing *(proven entity) generated about 275lbs of downforce at 120mph at a 7 degree setting (more like 15 including the roof line flow degrees added in)

mark kibort

this is what i was thinking. hog out the mettal. paint the base black and then it looks just like it should and functions that way too.

jbrob007

Carl,

Effective to me is redirecting the air over or around (instead of under) with enough additional downward force at "reasonable" speeds (under 100 mph) to help the car handle & stick to the road better - especially in curves. I hope that doesnt sound too "lawyerish..."

Mark,

Hopefully I'm interpreting your comments correctly. If the support is sticking out this far and is solid then it may inhibit the air from being diverted AROUND the car... correct? If so, then it makes perfect sense to me... If not, then I'm lost - which doesnt take much

mark kibort

Joel,

Exactly. the air normally is diverted from the nose downward, what ever doesnt enter the radiator opening, goes under the car, as that is the differential pressure that the air moves too however, if you have a splitter, the air bunches up around the nose and bleeds to the sides. thats the primary reason a splitter works. that air now, instead of going under the car, is diverted to the sides. it does this with VERY LITTLE force on the splittet itself. its not a wing, its a spliter and works much differently. conversely, if you have a huge mouth opening, and can have a clean path of air flow through the radiator and out the hood, to a lower pressure zone, that is even MORE effective. two reasons those extra air molecules are added to the above air flow. speed stays the same, but the mass flow is creater, and this creater mass now hits the rear wing and makes it more effective too.

the brakets as they are, will create a road block for the air traveling to the sides , its pressure will increase there and find its way under the car , and /or force more into the radiator, which feeds under the car in most cases, reducing downforce. so making them cleaner is the way to go. knowing that the forces on the splitter are never more than .35psi for speeds over 160mph, shows that the 300sq" splitter only needs to have about 100lbs of support, unevenly distributed over the entire plank. ( most splitters for our cars are about 48" x 6" ) what Carl found, was even at that speed, he got over 3-500lbs of downforce up front, maybe more. he clamied 100bs at 40mph, so that means he might have got near 400lbs at 80mph and near 1600lbs at 160mph, which is all from the diversion of the air flow and the air flow over the car, and not directly applied to the splitter.

key to the design, Carl will want to pin the "tilt up " feature, as that could be deadly, if you are really using the splitter at speed. Its a great design and looks pretty simple to install. with these two mods, its complete and will look better, be safer and more effective than it already is.

Carl Fausett

Not ignoring this thread... there are some posts I'd like to respond to.
Swamped in the shop and dont have the keyboard time I'd like.
I will try to contribute when I can.

mark kibort

So, on to the other misconception. cooling. Carl, Brian, the splitter will not effect cooling. again, one of those intuitive things that might point to a configuratoin that "guides" the air into the radiator bettter, but it doesnt. the flat plate pressure is the max pressure you will get at any speed. the pressure head in front of the radiator, doesnt change, and that is how air moves. it moves to differnetial pressure. however, a hood vent, reduces the restriction on the exit area of the air flow, and that CAN increase cooling flow by quite a bit. (air now, goes under the car, but also goes over the car though the hood vent. putting a splitter on would seem to frame the "air" bunching up at the nose, but in actuallity, it doesnt change the pressure in front of the radiator. IT only diverts (splits ) the air that would normally go under the car and routes it to the sides.
if you saw "vast" improvements to cooling, it was done to something else.

the max pressure you can get at the nose of the car is .11psi at 80mph. this might be seen at the face of the radaiator. you an improve this by framing, or funneling air to the radiator.

M

jbrob007

"Exactly"... WOW!!! I must be a GENIOUS!!! LOL! I'm going to consider this (once my car $$ account is back up to par) as it seems to be a worthwhile investment and not too expensive. It seems to me that if Carl made the modifications to the supports as Mark suggests then it would also fit better under a stock chin spoiler (I have an 86.5). Maybe even without having to modify the spoiler (or at least not too much) which would be preferable in may case.

Thanks for the detailed discussion guys. I've learned ALLOT... again

brutus

If you are looking for higher cornering speeds which is the ONLY place downforce is of any benefit for a street car far better to work on better tires/wheels/suspension. The only good use for this "splitter" would be for plowing snow in the winter time. You already have 3500 lbs of downforce from the weight of you and the car another 100-200 lbs adds little to the equation. And few ever really drive any car on the street at anything near the limits of a 928s cornering ability.

Carl Fausett

My understanding was they were available in europe. But it really doesnt matter.

If it helps you, I can just say "get a set of 78-82 front spindles from 928 International" and leave it at that.

mark kibort

so true, but this does have a cool factor if it is cleaned up as I suggest. however, remember, you might have 3500lbs of downforce straight, but when you corner, that is working against you to a greater degree, so a splitter is the life safer there, at very high speeds.

Carl, I think a F1 car has 100lbs of downforce at 40mph, but if you saw it, i sure would like to know how. the pressure differntial to create that kind of downforce doesnt seem to be possible with a 928, even with splitters and wings, unless it happens naturally with out the wings and splitters..

check out this great video of a known entity in the racing world getting put on the dynos. i was running with this car at a time attack. it was faster than a speed GT front runner. check ou tthe wind tunnel tests they did.

IcemanG17

My walmarts finest airdam (thanks Rich) is NOT a splitter....its an airdam that stops air from going under the car....so where does it go? It will go to the path of least resistance.....which is sucked into the car, through the radiator and out the hood vent.... the only other paths are forward, against pressure up and over the bumper...which isn't going to happen....or down, under the car...which where some air clearly goes....

I ran on track for almost 2 hours today....at ambient temps from the 40's to 60's....I never saw a radiator temp above the 1st white line on the stock gauge or about 155F on my digital gauge....

Worked good enough for a personal best lap time of 2:06.52 over the top at Thunderhill.... Not bad for a station wagon automatic....

mark kibort

Brian, dont let intuition gude you with air flow. alll things being eqaual, when you are going 60mph, the air fow through the radiator is at a the rate that the pressure drop allows. putting an air dam or spliter doesnt change the pressure at the nose. no more air flow s through the radaitor. air moves to differential pressure. you are not raising the pressure at the nose, but what you are doing is not leting the air go under the car , by broadening the pressure zone with more of the same pressure air as before. where does it go, to the sides. thats what air dams do. same as splitters, but not as effective for the same hieight off the ground. BUT, a very low air dam, can be near as effective as a much higher positioned splitter.
you can verify what im saying with a simple pressure guage on the fron and then the rear of the radiator. if the pressure diff doesnt change, then there is no more flow. trust me, you may think its making the car run cooler, but thats more a factor of maybe less air in the system or your hood vent, which will help in more efffective cooling.

i run so cool with 160 more hp than you , with a stock radiator and no fans runnning on even warm days!

Vlocity

I used a set of Carl's skid plates as the mounting point. I've been running this set up now on track for two years. My splitter has a central area that allows for some additional cooling to the oil pan. Last pic is the cardboard mock up.

I do like the composite over my aluminum. I've "mowed" with mine and hit a racoon on the highway at 65 MPH...but no big offs
where the splitter really would dig in.

Link to vent

https://rennlist.com/forums/showthre...ferrerid=19521

Link to splitter

https://rennlist.com/forums/showthre...ferrerid=19521



Ken